Spaceflight

The Kosmos 482 spacecraft launched from the Baikonur Cosmodrome, now part of Kazakhstan, aboard a Molniya rocket on March 31, 1972. A short time later, the rocket's upper stage was supposed to propel the probe out of Earth orbit on an interplanetary journey toward Venus, where it would have become the third mission to land on the second planet from the Sun.

But the rocket failed, rendering it unable to escape the gravitational grip of Earth. The spacecraft separated into several pieces, and Russian engineers gave up on the mission. The main section of the Venus probe reentered the atmosphere in 1981, but for 53 years, the 3.3-foot-diameter (1-meter) segment of the spacecraft that was supposed to land on Venus remained in orbit around the Earth, its trajectory influenced only by the tenuous uppermost layers of the atmosphere.

The Aerospace Corporation's experts predict Kosmos 482 will fall to Earth some time nine hours before or after 1:54 am EDT (05:54 UTC) Saturday. The European Space Agency's forecast is centered on 3:12 am EDT (07:12 UTC) Saturday, plus or minus 13.7 hours.

The reentry windows will narrow over the next couple of days, but experts won't be able to pinpoint an exact time or location before the spherical spacecraft makes its final plunge.